CVE-2026-40687Network attack vector

Connection-process crash and heap disclosure via SPA buffers

Published Apr 30, 2026 · Updated Apr 30, 2026

Memory corruption in Exim before 4.99.2 allows remote attackers to crash a connection process or read uninitialized heap data via SPA. The SPA decoder leaves its destination buffer uninitialized, while SPA field builders copy attacker-controlled data into fixed buffers without complete bounds enforcement. Exploitation requires the SPA driver and a hostile or compromised SPA/NTLM peer; impact is limited to the connection process and heap data exposed to that peer.

CVSS severity4.8
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Exim before 4.99.2 allows remote attackers to crash a connection process or read uninitialized heap data via SPA. The SPA decoder leaves its destination buffer uninitialized, while SPA field builders copy attacker-controlled data into fixed buffers without complete bounds enforcement. Exploitation requires the SPA driver and a hostile or compromised SPA/NTLM peer; impact is limited to the connection process and heap data exposed to that peer.

The record

CVE
CVE-2026-40687
Published
Apr 30, 2026
Updated
Apr 30, 2026
Vendor
LibSPF2 Project
Product
Exim
Classifications
CWE-909, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <4.99.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LibSPF2 Project · Eximversion=0 <4.99.2

Published CVSS scores

9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
4.8MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-909Missing Initialization of Resource
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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